Argenteuil, a town of France, in the department of Seine-et-Oise, on the Seine, 5 m. N. W. of Paris; pop. in 1866, 8,176. It carries on an active trade in wine of inferior quality. Among the adjoining country seats is the chateau du Marais, formerly owned by Mirabeau. The town originated from the convent or priory of Argenteuil founded in the 7th century, and converted by Charlemagne into a nunnery, of which Heloise became abbess, after having been educated and taken vows there. Its ruins are still extant.